I've lurked around here for a couple of years now and have been looking for the right car. I'm going to look at a 350SD in a couple of days. It's a rod bender with 161,000 miles on the clock. If it's half as nice as the owner says and I crawl under it and can see the engine tag and it's a 3.0, then I'm going to be $4,000 poorer but with a big grin on my face. Supposedly EVERYTHING works on the car and it has no cracks in the dash or the seats.

I'm trying not to get my hopes up too much. Up until a year ago it was with the original owner and the current owner's wife says it's too big for her and she wants a TDI Jetta.

My question here is, what if it's the original 3.5, do I trust it or not.

Steve

Good question, only suggestion I have, do a search for 350sdl WIKIPEDIA, I remember reading something there one time about serial numbers in the productions run, something about those after a certain number are the "new and improved" models. I dunno, just making a suggestion...

Give this thread a read.

FWIW the flat surface by the injection pump that should have the engine number is totally blank on my engine.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Mine too.

__________________

Gone to the dark side

- Jeff

It sold before I could go see it. Oh well, the search will continue.

A replacement MB block or engine won't have a number by the IP. It should have a tag at the aft end of the block on the turbo side below the block heater. IIRC the 7th and 8th digits tell you if it was a replacement short block (no head), long block or complete engine. Here's a sample tag from gsxr's collection:







I don't know how Metric and other rebuilders identify reworked 603s.

If you don't mind the work of replacing the engine, don't dismiss an iffy 3.5. You can swap in a 3.0 block for little more than the cost of a good short block and a head gasket. Under $1000 bare bones to $2500 if you succumb to while you're in there's. Don't make a decision without pulling the head to measure piston protrusion to confirm bent rods. A bad head gasket oil seal will cause symptoms of a bent #1 rod.

Sixto
87 300D

I have 13,500k on my 1991 350SD.
The rods were replaced by MB at no cost to me 8 years ago.
Due to the high compression they bend. They were re-cast with more metal on the lower end. Dealer got paid for the work directly by MB.
Never had problems since.
If it runs well now & is not driven a lot at high speeds (more than 75mph) steady like on a turnpike, often, it SHOULD be OK.

I'm curious why steady speeds >75mph would hurt the engine?

__________________

Gone to the dark side

- Jeff

I don't buy the whole undersquare / oversquare argument. All VW diesel engines are undersquare, just like the 350, and they'll rev all day long. When I'm on the highway my ECOdiesel spends long times sitting at 4200 RPM... a 4.25:1 diff will do that for ya No bent rods yet.

IMHO the problem resulted from a poor quality casting in the original rods.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Can the tag be found in the same place on a .971 replacement in W140 cars?

Thanks
Steve A

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Steve A
92 W140 OM603
97 VW Jetta TDI
90 Passat variant TDI 6 speed MT
94 Chevy K1500 6.5TD
05 E320 CDI
+ others

My car ran at 90-100 for about 300 miles earlier in the week through the mountains. Seems fine.

Would running a cetane booster help prevent rod bending? Mercedes said they didn't have rod bending problems in europe where the cetane ratings are higher.

Higher cetane fuel is never, ever a bad thing.

-J

In my area- texas has moved away from the 42 cetane for quite sometime.

I think the new min is 48 or 50 cetane. So it's probably inline with the factory design at the time.

FYI I don't believe those are cast rods- yes the replaements are beefier. They also beefed up the piston and pin.

I think oversquare or undersquare is not the issue. It's the rod length/stroke ratio puts greater side-wall pressures due to geometry.


FYI I'm still looking for a used 3.5 liter crank if someone is de-stroking an engine.

Michael

My car runs like crap when not on cetane booster, the change is very obvious.

I believe so.

Sixto
87 300D